1. Field of the Invention
The present invention relates to the coiling of a substantially continuous length of textile material, in the form of thread, hereinafter generically referred to as yarn or thread. More particularly, this invention relates to an apparatus for producing a coiled yarn package by feeding loops of yarn on a receiving plate in such a manner that the loops progress along a substantially annular path.
An apparatus for producing a coiled yarn package, of the type above mentioned, is described in my U.S. Pat. No. 3,816,889, issued June 18, 1974.
2. Description of the Prior Art
In the prior art there are known apparatuses for producing a coiled yarn package of the mentioned type, which basically comprise a receiving plate upon which a depositing disc deposits the yarn in loops, there being provided a relative movement between the depositing disc and the receiving plate, so that the loops progress along an annular path to form successive layers of yarn.
The receiving plate and the depositing disc are elastically urged the one towards the other, so that the yarn is actually drawn, from suitable supply means to a through bore provided in the depositing disc, by the combined action of the rotating depositing disc and of the receiving plate, from which it is clamped while being deposited in loops. This is due to the fact that the underside of the depositing disc, which is constructed with such a diameter as to cover the whole upper surface of the package being formed, has the lowest possible frictional coefficient, while the receiving plate and the upper surface of the package being formed present a higher degree of adhesion or sticking capacity with respect to the frictional resistance generated by the side of the depositing disc which is in contact with the yarn package being formed.
Basically, the formation of a yarn package of the type above described can be accomplished in two ways. According to a first mode of operation, a rotating thread-depositing member or depositing disc is provided having a fixed axis of rotation, from which the thread is deposited in circular rings. Since however also the surface onto which the thread is deposited is rotating about an axis which is eccentric with respect to the axis of rotation of the depositing member, the thread will be deposited onto the receiving surface or plate in loops which progress along an annular path.
According to a second mode of operation, the receiving surface does not rotate, while the thread depositing member or depositing disc, besides rotating about its own axis, revolves also about a fixed axis which is eccentrically arranged with respect to its above mentioned axis of rotation, i.e. the axis of rotation of the thread depositing member rotates about a fixed spaced-apart axis, which coincides with the center of the package being formed.
In any case, as appears evident from the above, it is necessary to provide for a relative circular movement between the receiving plate and the axis of rotation of the depositing disc.
In the prior art apparatus according to U.S. Pat. No. 3,226,794 (ERB) the thread is drawn from the supply bobbin following to the above mentioned relative movement between the receiving plate and the axis of the depositing disc, due to the mentioned friction or sticking capacity which exists between the thread being deposited and the surface of the receiving plate or of the latest layer of yarn loops which has been deposited. Thus, the draw-off force which is necessary for drawing the yarn from the supply bobbin, is directly exerted on the said latest layer of yarn loops which has been deposited. It may happen therefore, particularly, in the case of smooth yarns for example of synthetic fibers, that this draw-off force, directly exerted on the yarn layers already deposited, greatly disturbs the formation of regular loops, and, consequently, the formation of a yarn package having the desired characteristics.
In order to overcome the mentioned inconveniences, and to increase the clamping force with which the thread is clamped between the depositing disc and the receiving plate (or latest deposited layer of loops) it has been proposed, in the mentioned U.S. Pat. No. 3,226,794, to provide a contact element for pressing the thread being deposited onto the receiving plate, said contact element being arranged on the rotating depositing disc and acting through said disc through any conveniently provided bore or slot. The mentioned contact element may have the form of a curved leaf spring, or of a roller journalled onto said depositing disc. In both cases, the pressure action of the contact member which projects into the package beyond the surface of the depositing disc, disturbs the formation of the package, and, whenever it is necessary to provide on the depositing disc a slot larger than a simple through bore, such as for example it is required in the case of the roller, also the presence of this slot or aperture disturbs the regular formation of the package.
In the prior art apparatus according to U.S. Pat. No. 3,478,399 (WYATT) there are provided, between the supply bobbin and the through bore in the depositing member, a pair of feed rollers, which thus draw off the thread from the supply bobbin and feed it at the desired speed to the depositing member.
In the prior art apparatus according to Italian Pat. No. 941,625 (CROTTI) the positive feeding of the yarn at the exact speed which is required by the drawing action of the depositing disc and of the associated receiving plate is obtained by providing a feeding roller which is integral in rotation with the depositing disc, and travels along a fixed annular track. The yarn to be fed to the through bore in the depositing disc is clamped between the feeding roller and the annular track, so as to be positively fed to the through bore in the depositing disc, upon rotation of the said depositing disc.
However, in the apparatuses of the two latest mentioned devices (U.S. Pat. No. 3,478,399 and Italian Pat. No. 941,625), though same operate in a satisfactory manner, there is the problem that the feed rollers are devices which operate at high speed, and therefore are subject to all the disadvantages associated with this type of devices, disadvantages which originate from the connected problems of the bearing, lubrication and, if requested, driving into rotation of the said rollers.